Fighter training, the F16, and a math/physics question

[snowman]

I live in a corridor right between an Air National Guard unit, the 180th Fighter Wing, and Wright Patterson Air Force Base at Dayton. Consequently I get to hear these fellows fly over quite often, especially when they are doing training maneuvers, which are very often right overhead. They still use the F16 as far as I know(one flew right out of a cloud last year when I was watching off my front porch). Some years ago I got to see the Thunderbirds who, at that time at least, were using the F16 as well. I remember being very impressed with the maneuverability of the plane.

Anyway I got curious the other night and thought I would look up the specs. I noted that the weight of the plane was listed at 37,500 lb, and the thrust of the engine was listed at 27,000 lb.

Since I'm not accomplished in math and science, and know that many of you are, I thought I would ask a question here. In my simple but faulty thinking, it seemed to me that thrust would have to exceed the weight of the plane in order for it to do what it is called upon to do(especially execute a vertical climb). Educate me here; what do I need to know?

Thank you, friends.
Andy

 

[ContinentalOp]

Neither a pilot nor an engineer, but I was curious and looked it up. According to Wikipedia, the empty weight of the F16 is 18,000lbs, the gross weight is 26,500lbs, and the thrust is just over 29,000lbs, depending on the engine. So it's conceivable for the thrust-to-weight ratio to be greater than 1, allowing for vertical climbing.

General Dynamics F-16 Fighting Falcon - Wikipedia (Specs are at the bottom of the page.)

 

[snowman]

How about that. I just typed in "f16 specs", and was given the figures in the first post -apparently some of Wikipedia's contributors erred. The specs you gave are much more detailed and extensive; I would sooner believe those.

Thanks for the response.
Andy

 

[rkittine]

You have to remember that the wing provides considerable lift. A light plane weighing 1600 pounds can still got over 100 knots with a 145 hp engine. You can hand push your 2000 pound boat when it is in the water.

 

[Dougaz]

As time allows, check out the new Boeing F-15EX ..... What a fighter this bad boy is!

 

[DWalt]

If a F-16 transitions from high-speed horizontal flight to an upward trajectory, there is considerable inertia assisting it to climb. Also, using the afterburner would add additional thrust.

I once saw an F-15 do exactly that. It went into a vertical climb with afterburners lit up and it went nearly out of sight.

 

[LVSteve]

The Thunderbirds run their airplanes light, so they probably have a thrust to weight ratio in excess of one. A mission loaded F-16 is not so lucky. The F-15C does exceed one (just) at a gross weight of 44,500 lbs and thrust of 23,500 lb x 2.

 

[Bro. Dave]

I've always taken it all on faith. I remember reading that bumblebees shouldn't be able to fly, either!

 

[Absalom]

I'm a horrible physics teacher, but as has been indicated already, pounds of thrust and pounds of weight are not in any linear, direct relationship. The thrust translates into forward speed which generates lift via the airfoil shape of the wings. A plane is not a rocket, where the thrust lifts the craft directly.

A single-pilot glider produces no thrust at all, usually weighs between 500 and 1000 lbs. and still flies just using gravity, and thermals for climbing.

PS: Apparently the F-15 was the first plane with sufficient thrust to sustain and accelerate in a vertical climb. In that particular situation, the engines have to function like a rocket and be able to lift the plane's weight. Earlier jets had to zoom-climb, that is, use momentum and trade speed for altitude as they climbed vertically, eventually topping out.

I'd imagine that's what they still do if their actual weight exceeds their available thrust, due to fuel or weapons load.

 

[MRB1]

One of the requirements of the Air Force using the F-16 for the Thunderbirds was the planes could be capable of being returned to service almost immediately. The only difference between a in-service A/C and a T-Bird is the ammo drum on production A/C was removed and replaced with a specially designed fuel bladder. The drum can be replaced very quickly. The wings, although still IR (interchangeable/replaceable) are as close to perfect as production allows. A special wing assembly line was formed using the most qualified, experienced employees. We're almost talking zero defects here. Otherwise, the planes are the same.

 

[ContinentalOp]

You have to remember that the wing provides considerable lift. A light plane weighing 1600 pounds can still got over 100 knots with a 145 hp engine. You can hand push your 2000 pound boat when it is in the water.

I'm a horrible physics teacher, but as has been indicated already, pounds of thrust and pounds of weight are not in any linear, direct relationship. The thrust translates into forward speed which generates lift via the airfoil shape of the wings. A plane is not a rocket, where the thrust lifts the craft directly.

A single-pilot glider produces no thrust at all, usually weighs between 500 and 1000 lbs. and still flies just using gravity, and thermals for climbing.

Except OP is asking about vertical climbing. In that case, the F16 is going to be more like a rocket than a plane, and thrust-to-weight is going to be a lot more important than the lift of the wings.

 

[Onomea]

Seems to me I read somewhere that the F15 was the first plane — only plane? — to break the sound barrier going straight up. (Must be a mighty sporty ride!)

 

[Rustyt1953]

I grabbed this from the web:

TWR or T/W ratio = (Max Thrust of Engine / (Empty Weight + (3.505 Tonnes of Fuel & Weapons, or only Internal Fuel)))

1.30 - Su-35S
1.29 - F-15K
1.26 - Su-27S
1.25 - Eurofighter
1.24 - Mig-35 (T/W = 1.45 during Emergency Thrust*)
1.23 - Su-27SK & J-11A
1.19 - Mig-29M/M2 (T/W = 1.39 during Emergency Thrust*)
1.19 - F-15C
1.18 - F-22A (T/W = 1.37 with Round nozzles?)
1.16 - Su-30MKK

1.16 - Rafale C
1.16 - F-35A
1.15 - Mig-29B (9-12)
1.14 - Su-30MKI (T/W = 1.21 during Emergency Thrust@)
1.13 - Mig-29 (9-13), S, SD, SE & SM
1.11 - F/A-18E (F/A-18F: 1.09)
1.10 - Rafale M
1.10 - Mig-29 BM & SMT (T/W = 1.15 during Emergency Thrust*)
1.09 - F-16E Block 60
1.09 - Mig-29K (T/W = 1.28 during Emergency Thrust*)

 

[snowman]

Except OP is asking about vertical climbing. In that case, the F16 is going to be more like a rocket than a plane, and thrust-to-weight is going to be a lot more important than the lift of the wings.

Correct. I should have been clearer. One of the things that I appreciated so much about the Thunderbirds' show was their emphasis in demonstrating, not just their ability as pilots to perform daredevil maneuvers, but also the capabilities of the plane itself.

I remember distinctly when I watched the Thunderbirds' show that one of them performed the vertical climb exactly as outlined by Absalom in describing the F15. The show was over Lake Michigan, and he came in from the north at low to moderate speed, pointed the thing up right in front of us and drew the rear end directly underneath him so he was nearly perpendicular to the surface of the water. Then he put the hammer down so to speak and flew straight up(with a bit of a spiral movement) into the clouds.

Coincidentally, one of the men in our group said to his son while observing this maneuver, "It's no longer a plane; it's a rocket." So the F16 appears to have that capability, without assistance from horizontal momentum or the wing. The clouds were high that day; he wasn't much more than a dot by the time he completed his climb. Momentum would have been exhausted, I would think, long before he leveled off.

So I'm guessing that the afterburner made the difference. Anyone know roughly how much thrust, percentage-wise, those things add to the equation?

Regards,
Andy

 

[fordson]

Depending on the aircraft/engine combinations, "Zone 5" Afterburner (J79 engines in F-4 Phantom) can add close to 40% more thrust. And you can also watch your fuel gauge drop to near zero, thereby making the aircraft lighter which in turn improves your Thrust to Weight ratio which then increases your acceleration which then...............

 

[rkittine]

With full afterburners I could climb an F4C vertically for a brief period using initial momentum to help. Would be interesting to see which current aircraft could launch vertically from a stationary vertical support as a missal would.

Bob

 

[LVSteve]

All you need is thrust.

Zero-length launch - Wikipedia

 

[Rastoff]

You have to remember that the wing provides considerable lift.

Except that an F-16 wing provides very little lift.

The OP's info on weight and thrust is wrong. The F-16 definitely produces more thrust than it has in weight. If it didn't it wouldn't fly at all.

The F-16 has almost no glide ability. If the engine dies and cannot be restarted, the pilot must eject. The plane cannot be glided to the ground; it just falls.

The wings on an F-16 are configurable. The amount of lift can be adjusted. The leading edge of an F-16 is variable and can actually create a negative lift situation which is why it can fly upside down almost as easily as right side up.

The plane that's really impressive is the F-22. It has a thrust to weight ratio of 1:1 at cruise and 1:1.25 at full AB. Add the vectored exhaust and it's beyond amazing. The F-35 is not as powerful as the F-16, but has more capability.

I feel fortunate that I can see these planes fly regularly. It's an air show every day where I work.

 

[snowman]

The OP's info on weight and thrust is wrong. The F-16 definitely produces more thrust than it has in weight. If it didn't it wouldn't fly at all.

Ah, so my thinking was correct; thank you. I had heard that Wikipedia's information wasn't always to be trusted, but this is the first time I've run across a definite error.

The plane that's really impressive is the F-22. It has a thrust to weight ratio of 1:1 at cruise and 1:1.25 at full AB.

So "1" is actually the greater quantity in "1:1.25"?


Thanks,
Andy

 

[LVSteve]

Ah, so my thinking was correct; thank you. I had heard that Wikipedia's information wasn't always to be trusted, but this is the first time I've run across a definite error.



So "1" is actually the greater quantity in "1:1.25"?


Thanks,
Andy

Those proportionalities are the wrong way round for me. I would say that 1 should always be the second item, so the F-22 thrust-to-weight ratio is 1.25:1.

I'm also thinking that Rastoff has got lift and thrust mixed up a little. Also, thrust to weight will change dues to weapon and fuel load. For sure the ones that come out of Nellis fully equipped with multiple tanks and stores aren't going up as quick as the Thunderbirds during practice.

As for the glide capabilities of the F-16, pretty much all jets from the 60s on have the glide characteristic of a brick. The F-16 is likely handicapped by its very unstable design. If the motor goes down and takes the fly-by-wire system with it, it becomes a falling leaf in short order.